Throughout this specification, when discussing the application of this invention to the aorta or other blood vessels, the term “distal”, with respect to a prosthesis, is intended to refer to a location that is, or a portion of the prosthesis that when implanted is, further downstream with respect to blood flow; the term “distally” means in the direction of blood flow or further downstream. The term “proximal” is intended to refer to a location that is, or a portion of the prosthesis that when implanted is, further upstream with respect to blood flow; the term “proximally” means in the direction opposite to the direction of blood flow or further upstream.
The functional vessels of human and animal bodies, such as blood vessels and ducts, occasionally weaken or even rupture. For example, the aortic wall can weaken, resulting in an aneurysm. Upon further exposure to hemodynamic forces, such an aneurysm can rupture. In Western European and Australian men who are between 60 and 75 years of age, aortic aneurysms greater than 29 mm in diameter are found in 6.9% of the population, and those greater than 40 mm are present in 1.8% of the population.
One surgical intervention for weakened, aneurismal, or ruptured vessels involves the use of a prosthetic device to provide some or all of the functionality of the original, healthy vessel, and/or preserve any remaining vascular integrity by replacing a length of the existing vessel wall that spans the site of vessel failure. One such prosthetic device is a stent graft. Stent grafts are used for treatment of vasculature in the human or animal body to bypass a repair or defect in the vasculature.
A length of a vessel which is treatable by such a prosthesis may have one or more branch vessels, i.e. vessels anastomosed to the main vessel. The celiac artery, superior mesenteric artery, left common carotid artery, and renal arteries, for example, are branch vessels of the aorta; the hypogastric artery is a branch vessel of the common iliac artery. Thus, a stent graft may be used to span an aneurism which has occurred in or is associated with the primary artery. Bypassing such a branch vessel without providing blood flow into it can cause problems and hence it has been proposed to provide a fenestration or a side branch on a stent graft which when deployed is positioned over the opening to the primary artery and then another stent graft can be deployed through the fenestration or side branch into the secondary artery to provide a blood flow path to the secondary artery.
When treating a vessel with a prosthetic device, it is therefore preferable to preserve the original circulation by providing a prosthetic branch that extends from the prosthesis to a branch vessel so that the blood flow into the branch vessel is not impeded. For example, the aortic section of one abdominal aortic prosthesis can be designed to extend above the renal arteries and to have prosthetic branches that extend into the renal arteries. Branch extension prosthetic modules (“branch extensions”) can form a tromboning connection to the prosthetic branch to complete the prosthesis. Furthermore, some aneurysms extend into the branch vessels themselves. Deploying prosthetic branches and branch extensions into these vessels may help prevent expansion and/or rupture of these extended aneurysms.
Another example of a vessel that may be treated with a stent graft is the aortic arch. Aortic arch stent grafts are used in treating dissection and aneurismal dilation of the aortic arch. As with other primary vessels, many of these grafts have branches that maintain the patency of the branch arteries originating in the aortic arch. These branch arteries include the innominate artery, the left common carotid artery, and the left subclavian artery. A stent graft in the aortic arch may itself be branched to help direct the flow of blood into these branch arteries. Many of these branched grafts have branches that project outward from the prosthesis. Implanting the stent grafts in the branch arteries provides a challenge to surgeons because of the anatomic features of the aortic arch. Blood flow from the branch arteries must not be interrupted for an extended length of time because the branch arteries supply blood to the brain. Implanting branch stents that mate with the branches presents challenges because the natural orientation of the aortic arch must be matched or simulated by the stent grafts.
A surgeon may access the aortic arch through the branch arteries to implant small vessel stents. Guide wires are used to link the small vessel stents in the branch arteries with the branches of the aortic arch stent. However, much time may be lost in threading the guide wires through the openings of the aortic arch stent branches and through the branch arteries. A surgeon will often manipulate the guide wire around the difficult angles in the aortic arch stent channels before being able to connect with the delivery catheter of the branched stent.
In general, manipulating guide wires to correctly and reliably position a medical device such as a stent graft requires the surgeon's utmost skill and experience. The surgeon has relatively little information available defining where the medical device is positioned, its orientation and alignment. Conventionally, fluoroscopy has been used by surgeons to obtain real-time moving images of a patient's anatomy. However, the use of x-rays for fluoroscopy poses a health risk to the patient, the surgeon and other medical personnel. Because of small geometries, placement accuracy can be critical, particularly when positioning a device such as a stent graft in relation to another vessel such as a branch artery. There is therefore a need for an improved method and device for providing information to the surgeon about the position and orientation of the medical device. Moreover, there is a need for doing so using safer techniques that reduce the use of fluoroscopy.